DESCRIPTION

Get or set a unique 32-bit identifier for the current machine. The
32-bit identifier is intended to be unique among all UNIX systems in
existence. This normally resembles the Internet address for the local
machine, as returned by gethostbyname(3), and thus usually never needs
to be set.
The sethostid() call is restricted to the superuser.
The hostid argument is stored in the file /etc/hostid.

RETURNVALUE

gethostid() returns the 32-bit identifier for the current host as set
by sethostid().

FILES

/etc/hostid

CONFORMINGTO

4.2BSD; these functions were dropped in 4.4BSD. SVr4 includes
gethostid() but not sethostid(). POSIX.1-2001 specifies gethostid()
but not sethostid().

NOTES

In the glibc implementation, if gethostid() cannot open /etc/hostid,
then it obtains the host name using gethostname(2), passes that host
name to gethostbyname_r(3) in order to obtain the host’s IPv4 address,
and returns a value obtained by bit-twiddling the IPv4 address. (This
value may not be unique.)